Re: [PATCH v2 net] dccp/tcp: do not inherit mc_list from parent

[Eric Dumazet]

On Tue, 2017-05-09 at 15:37 -0700, Cong Wang wrote:
> On Tue, May 9, 2017 at 6:29 AM, Eric Dumazet  wrote:
> > From: Eric Dumazet 
> >
> > syzkaller found a way to trigger double frees from ip_mc_drop_socket()
> >
> > It turns out that leave a copy of parent mc_list at accept() time,
> > which is very bad.
> >
> > Very similar to commit 8b485ce69876 ("tcp: do not inherit
> > fastopen_req from parent")
> >
> > Initial report from Pray3r, completed by Andrey one.
> > Thanks a lot to them !
> >
> > Signed-off-by: Eric Dumazet 
> > Reported-by: Pray3r 
> > Reported-by: Andrey Konovalov 
> > Tested-by: Andrey Konovalov 
> > ---
> > v2: fix moved into inet_csk_clone_lock() to fix both DCCP and TCP
> >
> >  net/ipv4/inet_connection_sock.c |2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/net/ipv4/inet_connection_sock.c 
> > b/net/ipv4/inet_connection_sock.c
> > index 
> > 5e313c1ac94fc88eca5fe3a0e9e46e551e955ff0..1054d330bf9df3189a21dbb08e27c0e6ad136775
> >  100644
> > --- a/net/ipv4/inet_connection_sock.c
> > +++ b/net/ipv4/inet_connection_sock.c
> > @@ -794,6 +794,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
> > /* listeners have SOCK_RCU_FREE, not the children */
> > sock_reset_flag(newsk, SOCK_RCU_FREE);
> >
> > +   inet_sk(newsk)->mc_list = NULL;
> > +
> > newsk->sk_mark = inet_rsk(req)->ir_mark;
> > atomic64_set(>sk_cookie,
> >  atomic64_read(_rsk(req)->ir_cookie));
> >
> 
> I think IPv6 needs this too?
> 
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index aeb9497..b3611d9 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1062,6 +1062,7 @@ static struct sock *tcp_v6_syn_recv_sock(const
> struct sock *sk, struct sk_buff *
> newtp->af_specific = _sock_ipv6_mapped_specific;
>  #endif
> 
> +   newnp->ipv6_mc_list = NULL;
> newnp->ipv6_ac_list = NULL;
> newnp->ipv6_fl_list = NULL;
> newnp->pktoptions  = NULL;

Good point, but it looks like you patched on only IPv4 mapped sockets.

And DCCP would need fixes as well.

Re: [PATCH v2 net] dccp/tcp: do not inherit mc_list from parent

[Cong Wang]

On Tue, May 9, 2017 at 6:29 AM, Eric Dumazet  wrote:
> From: Eric Dumazet 
>
> syzkaller found a way to trigger double frees from ip_mc_drop_socket()
>
> It turns out that leave a copy of parent mc_list at accept() time,
> which is very bad.
>
> Very similar to commit 8b485ce69876 ("tcp: do not inherit
> fastopen_req from parent")
>
> Initial report from Pray3r, completed by Andrey one.
> Thanks a lot to them !
>
> Signed-off-by: Eric Dumazet 
> Reported-by: Pray3r 
> Reported-by: Andrey Konovalov 
> Tested-by: Andrey Konovalov 
> ---
> v2: fix moved into inet_csk_clone_lock() to fix both DCCP and TCP
>
>  net/ipv4/inet_connection_sock.c |2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index 
> 5e313c1ac94fc88eca5fe3a0e9e46e551e955ff0..1054d330bf9df3189a21dbb08e27c0e6ad136775
>  100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -794,6 +794,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
> /* listeners have SOCK_RCU_FREE, not the children */
> sock_reset_flag(newsk, SOCK_RCU_FREE);
>
> +   inet_sk(newsk)->mc_list = NULL;
> +
> newsk->sk_mark = inet_rsk(req)->ir_mark;
> atomic64_set(>sk_cookie,
>  atomic64_read(_rsk(req)->ir_cookie));
>

I think IPv6 needs this too?

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index aeb9497..b3611d9 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1062,6 +1062,7 @@ static struct sock *tcp_v6_syn_recv_sock(const
struct sock *sk, struct sk_buff *
newtp->af_specific = _sock_ipv6_mapped_specific;
 #endif

+   newnp->ipv6_mc_list = NULL;
newnp->ipv6_ac_list = NULL;
newnp->ipv6_fl_list = NULL;
newnp->pktoptions  = NULL;

Re: [PATCH v2 net] dccp/tcp: do not inherit mc_list from parent

[David Miller]

From: Eric Dumazet 
Date: Tue, 09 May 2017 06:29:19 -0700

> From: Eric Dumazet 
> 
> syzkaller found a way to trigger double frees from ip_mc_drop_socket()
> 
> It turns out that leave a copy of parent mc_list at accept() time,
> which is very bad.
> 
> Very similar to commit 8b485ce69876 ("tcp: do not inherit
> fastopen_req from parent")
> 
> Initial report from Pray3r, completed by Andrey one.
> Thanks a lot to them !
> 
> Signed-off-by: Eric Dumazet 
> Reported-by: Pray3r 
> Reported-by: Andrey Konovalov 
> Tested-by: Andrey Konovalov 
> ---
> v2: fix moved into inet_csk_clone_lock() to fix both DCCP and TCP

Applied and queued up for -stable, thanks Eric.

[PATCH v2 net] dccp/tcp: do not inherit mc_list from parent

[Eric Dumazet]

From: Eric Dumazet 

syzkaller found a way to trigger double frees from ip_mc_drop_socket()

It turns out that leave a copy of parent mc_list at accept() time,
which is very bad.

Very similar to commit 8b485ce69876 ("tcp: do not inherit
fastopen_req from parent")

Initial report from Pray3r, completed by Andrey one.
Thanks a lot to them !

Signed-off-by: Eric Dumazet 
Reported-by: Pray3r 
Reported-by: Andrey Konovalov 
Tested-by: Andrey Konovalov 
---
v2: fix moved into inet_csk_clone_lock() to fix both DCCP and TCP

 net/ipv4/inet_connection_sock.c |2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 
5e313c1ac94fc88eca5fe3a0e9e46e551e955ff0..1054d330bf9df3189a21dbb08e27c0e6ad136775
 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -794,6 +794,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
/* listeners have SOCK_RCU_FREE, not the children */
sock_reset_flag(newsk, SOCK_RCU_FREE);
 
+   inet_sk(newsk)->mc_list = NULL;
+
newsk->sk_mark = inet_rsk(req)->ir_mark;
atomic64_set(>sk_cookie,
 atomic64_read(_rsk(req)->ir_cookie));